@izzythepush,
Honestly, Ive never had any thoughts about slate. i only did 2 jobs in my emntire career for companies involved in slate and both of them had itty bitty portions of their businesses i the rock (GAF used to grind slate up into tiny plates to spread over roofing felt to make asphalt shingles and they also had a division that made pool table tops.
I never saw marketing of slate as "the worlds best" Welsh slate is well known (as is Nazareth, Bangor, Reach Valley, Magog, and Peach Bottom). These are some slates from US and Canada mines. Slate is cool stuff and watching em cut it is fascinating.
Slate quarries are usually very stable rock bodies so they usually go verry deep down and Ive seen some 250 meters deep. Awesome places and one has to be very careful of the side dlopes because, since theres a lot of mica in the rock, the spoil piles and dust are slippery as fine mud except with oriented surfaces. Once they get wet, a slate pile is like a ski slope.
I once told my one client to thgink about using slate dust to pile on a slope for summer skiing.
Thats about all the opinions I have over slate
Although , it is best to keep a clean one handy.